remove restrictions on mapmodel rotation

Until now, the angles of mapmodels (and ctf-flags) were rounded to the
nearest 15-degree-step during rendering. This patch moves the rounding
to the time of placement of the model. Now the angle can be changed freely
after the model has been placed.

This commit also changes the angle resolution to 0.25 degree.

When changing the angle (press "1" + scrollwheel), additionally pressing
editmeta (a.k.a. LCTRL) changes the increments of the wheel from 1 to 10.

During a savemap with format 9, the angle resolution is reduced again, to
keep compatibility. Therefore, this features is only for testing right now.
It won't be preserved during a save (at least, as long as format 9 is used)
Keep selected player in op menus, when other player (dis)connects

Until now, when in, for example, kick player menu there was selected
some player and (dis)connected other player with lower CN, then this
earlier selected player was moved to other item in menu, but number
of selected item didn't change, so other player was selected.
Test work - ignore player menu
Add AssaultCube's CodeBlocks project for Linux
Don't show HUD reflection on water surface

For reflectclip > 1 player's HUD reflects on water surface.
Improve vote info

The commit:
1. adds additional small vote result for hidevote < 2, visible below radar,
2. sets default value of hidevote to 1,
3. shows final vote result in console.
Optimize and fix autodownload feature

The commit:
1. fixes value of download speed in KB;
2. introduces unique names of progress_callback() functions;
3. removes one unnecessary write_callback() function;
4. removes duplicated code/info in loadmodel().
Add altering pages in serverbrowser and improve favourites

Altering pages in serverbrowser are implemented with use favourites.
Categories (names) of favourite servers, which will be displayed on the
pages, have to be included in "serverbrowseraltpages" alias (accessible
in menu).
Switching between pages is possible with use ALT + mouse wheel or
"[", "]" keys.

The commit adds also MATCH category to favourites, shows category name
in settings of favourites and cleans up some tabs.
Add custom description of demos

Custom description is displayed in "Watching demo" and "Play demo" menu.