misc fixes and additions

[MosesofEgypt]

Issues closed:
#8
#3

Fixes:

• inability to run on newer python versions
• inability able to properly close and reopen new tags
• incorrect background color used for disabled boolean frames
• dxt bitmaps being recompressed to dxt when exporting to dds from viewer with full ARGB channels
• crash on linux when trying to use a BinillaWidget without a BinillaWidget tkinter.Tk root

Additions:

• ability to do Ctrl+A to select all in entry field on linux

Changes:

• binilla won't fail to generate widgets if one of the child nodes is corrupt
• better visual indication of invalid enumerator values