Unify show colors in tooltips and avatars

Both avatars and tooltips (contact list and and group chat participants list) display the contact's 'show' (e.g. online, away) colorized. In group chats there are additional colors involved when displaying a participant's affiliation (e.g. owner, admin). In order to reduce the number of colors, I removed affliliation coloring in the group chat tooltip. Participants are sorted by affiliation, so color does not add value here.

In the next step, colors are unified. At the moment, 'show' has the following values for tooltips, defined in config.py. Note the order of colors following the level of busyness:

• 'tooltip_status_online_color': #73D216
• 'tooltip_status_offline_color': #555753
• 'tooltip_status_free_for_chat_color': #3465A4
• 'tooltip_status_away_color': #EDD400
• 'tooltip_status_busy_color': #F57900
• 'tooltip_status_na_color': #CC0000

Gajim's avatar generator on the other hand works using the following color values:

• 'online': (102/255, 191/255, 16/255) rgb(102, 191, 16)
• 'offline': (154/255, 154/255, 154/255) rgb(154, 154, 154)
• 'not in roster': (154/255, 154/255, 154/255) rgb(154, 154, 154)
• 'chat': (102/255, 191/255, 16/255) rgb(102, 191, 16)
• 'away': (255/255, 133/255, 51/255) rgb(255, 133, 51)
• 'dnd': (230/255, 46/255, 0) rgb(230, 46, 0)
• 'xa': (106/255, 0, 242/255) rgb(106, 0, 242)

The following work has been done:

• removed unused get_css_show_color and corresponding css values
• added css colors for various show values (only 'online', 'away', 'dnd', and 'offline' -> colors from avatar generator)
• removed old color values in config.py
• added helper to allow avatar generator to use css values
• removed tooltip_idle_color, this can be added back if really needed
• removed tooltip_account_name_color, this can be added back if really needed
• made status colors configurable via theme