Move core docs back to core section; clean up titles

Requested by: https://github.com/QubesOS/qubes-doc/pull/823#issuecomment-497306277

doc.md

@@ -60,8 +60,8 @@ Core documentation for Qubes users.
  * [Getting Started](/getting-started/)
  * [Copying and Pasting Text Between Domains](/doc/copy-paste/)
  * [Copying and Moving Files Between Domains](/doc/copying-files/)
- * [Copying from (and to) dom0](/doc/copy-from-dom0/)
- * [Installing and Updating Software in dom0](/doc/software-update-dom0/)
+ * [Copying from (and to) Dom0](/doc/copy-from-dom0/)
+ * [Installing and Updating Software in Dom0](/doc/software-update-dom0/)
  * [Installing and Updating Software in VMs](/doc/software-update-vm/)
  * [Backup, Restoration, and Migration](/doc/backup-restore/)
  * [DisposableVMs](/doc/disposablevm/)
@@ -100,10 +100,14 @@ Core documentation for Qubes users.
  * [Storing AppVMs on Secondary Drives](/doc/secondary-storage/)
  * [RPC Policies](/doc/rpc-policy/)
  * [USB Qubes](/doc/usb-qubes/)
- * [Managing VM kernel](/doc/managing-vm-kernel/)
- * [Salt management stack](/doc/salt/)
+ * [Managing VM Kernels](/doc/managing-vm-kernel/)
+ * [Salt Management Stack](/doc/salt/)
  * [DisposableVM Customization](/doc/disposablevm-customization/)
- * [How to make any file in a TemplateBasedVM persistent using bind-dirs](/doc/bind-dirs/)
+ * [Making Any File Persistent Using `bind-dirs`](/doc/bind-dirs/)
+ * [GUI Configuration](/doc/gui-configuration/)
+ * [Resizing Disk Images](/doc/resize-disk-image/)
+ * [Troubleshooting UEFI](/doc/uefi-troubleshooting/)
+ * [Troubleshooting Newer Hardware](/doc/newer-hardware-troubleshooting/)
  * [KDE](/doc/kde/)
  * [i3 Window Manager](/doc/i3/)
  * [awesome Window Manager](/doc/awesome/)
@@ -227,9 +231,7 @@ Unofficial, third-party documentation from the Qubes community and others.
  * [Qubes Tips and Tricks](/doc/tips-and-tricks/)
  * [How to set up a ProxyVM as a VPN Gateway](/doc/vpn/)
  * [Multibooting](/doc/multiboot/)
- * [Resize Disk Image](/doc/resize-disk-image/)
  * [Changing your Time Zone](/doc/change-time-zone/)
- * [GUI Configuration and Troubleshooting](/doc/gui-configuration/)
  * [Installing ZFS in Qubes](/doc/zfs/)
  * [Mutt Guide](/doc/mutt/)
  * [Postfix Guide](/doc/postfix/)
@@ -255,14 +257,12 @@ Unofficial, third-party documentation from the Qubes community and others.
 ### Troubleshooting
 
  * [Home directory is out of disk space error](/doc/out-of-memory/)
- * [Newer hardware doesn't work](/doc/newer-hardware-troubleshooting/)
  * [Installing on system with new AMD GPU (missing firmware problem)](https://groups.google.com/group/qubes-devel/browse_thread/thread/e27a57b0eda62f76)
  * [How to install an Nvidia driver in dom0](/doc/install-nvidia-driver/)
  * [Nvidia troubleshooting guide](/doc/nvidia-troubleshooting/)
  * [Lenovo ThinkPad Troubleshooting](/doc/thinkpad-troubleshooting/)
  * [Apple MacBook Troubleshooting](/doc/macbook-troubleshooting/)
  * [Getting Sony Vaio Z laptop to work with Qubes](/doc/sony-vaio-tinkering/)
- * [Troubleshooting UEFI related problems](/doc/uefi-troubleshooting/)
  * [Fixing wireless on suspend & resume](/doc/wireless-troubleshooting/)
  * [How to remove VMs manually](/doc/remove-vm-manually/)
  * [Intel Integrated Graphics Troubleshooting](/doc/intel-igfx-troubleshooting/)