Separate themes from altyo_settings.vala to make them portable/extendable

[varemenos]

Themes are currently hardcoded into altyo_settings.vala and not defined in one location (there are the 16 length arrays and then there are the gtk css strings) and it makes it hard for someone to contribute new themes. It would be great if the themes were loaded from a directory where users could drop their own AltYo theme files to use.

[linvinus]

which version of altyo we are talking about?

Idea is good, but program style is not only css+color palette
These options affect the appearance
tab_format
tab_max_width
terminal_show_scrollbar
terminal_font
terminal_color_fg
terminal_color_bg
terminal_palette
terminal_opacity
terminal_background_image_file
terminal_background_fake_transparent
terminal_background_fake_transparent_scroll
terminal_tint_color
terminal_background_saturation
terminal_cursorshape
terminal_allow_bold_text
program_style
tab_title_format
tab_title_format_regex

in git trunk, options:
terminal_color_fg, terminal_color_bg, terminal_palette
also may be defined in css, but not other options.

hardcoded only predefined themes, you always may share/change your css style easily - by copy-paste.