Support a convenient way to load BED track into autocompletion.

[iromeo]

E.g. I have 50 BED tracks and I'm interested in bed entry names from one of tracks. Possible use cases: 1) load bed entry names into auto-completion. It is not reasonable to load all names from 50 tracks, because

• will be too many region names
• names could be same in different tracks, e.g. regions ids in DMR tracks are dmr-NNN. So is reasonable load into auto-completion only selected track, e.g. context menu action

2) show track regions + some flanking region in multiple location view. Currently BED track names are already in autocompletion, but for complex track names (e.g. HCS Consensus Methpipe our pipeline [1:200:1], M>20%) completion list will contain slightly different track name due to escaping, etc. + flanking not supported.

[iromeo]

3. as alternative to '1' show some special panel for navigation in track, there could be list of all regions + autocompletion. E.g. if I have 21 regions on different chromosomes - I'd like to iterate over them and look manually. Multiple regions view not very convenient here because I'd like to better see region neighbourhood.