Font file manager/browser, and new font handling

[nielsm]

Aegisub should perhaps have its own (integrated) font file manager and font browser, to manage large collections of fonts.
A font manager should ideally be implemented as a standalone application that integrated with Aegisub, such that it can also be used for other purposes.

As an extension of this, if Aegisub can some day scrap VSFilter entirely and depend only on other renderers, it could be viable to circumvent the system font libraries entirely and only work directly with font files through FreeType2. Aegisub would then manage a list of font files used for a project, make those available to the subtitle renderer, and allow managing that list with the font browser. This would make it even more portable and results much more predictable. It would also make the font collector obsolete.

[verm]

Bump 3.0.0 tickets to milestone:3.0.0 (2.2.0 is becoming 3.0.0)