fix: batch non-critical packages in single pacman call, drop old plasma theme, enable filesystem picker

Non-critical packages (Desktop/Plasma group, Utilities) went through try_install which installed them one-at-a-time (45 individual pacman calls). Override operation_try_install in PMPacman to batch all plain-string packages into a single call, matching the behavior of operation_install.

Also:
- Remove antergos-plasma-theme from rootfs (profile.yaml) and both netinstall Plasma groups
- Add allowFileSystemTypeSelection: true to both antergos and minimal partition.conf
- Both main.py files (profile + minimal) get the batching fix

iso-profiles/antergos/live-overlay/etc/calamares-online/modules/partition.conf

@@ -30,3 +30,4 @@ requiredPartitionTableType:
 
 defaultFileSystemType:  "ext4"
 availableFileSystemTypes:  ["ext4","btrfs","f2fs","xfs"]
+allowFileSystemTypeSelection: true

iso-profiles/antergos/live-overlay/etc/calamares/modules/netinstall.yaml

@@ -124,7 +124,6 @@
       description: "KDE Plasma Desktop"
       selected: false
       packages:
-        - antergos-plasma-theme
         - antergos-next-desktop-settings
         - ark
         - bluedevil