Rework advanced properties and hot reloading

[lperovskaya]

Add mapping from hot reloading structure to partisipant xml.

List with team ids (may be in contest.xml) (it's immutable).

Mutable list with special data (team video urls, team and cute full names, special start time).

[lperovskaya]

some examples that currently work:
team names, hashtag, groups, medias based on contestSystemId as a key
"teamOverrides": {
"486861": {"shortname": "ITMO test override","hashTag": "#ItMo","groups": ["SPb ITMO", "SPb"],"medias": {"camera": "localhost:12345/specialitmovideo","screen": null}}
}

"problemOverrides": {
"I": {"color": "#faeedd"}
}