Improve usability of tree-selection lists

[westram]

Access to trees in ARB is very primitive, esp. if one has stored many trees.

Improvements:

• provide additional columns (between 'name' and 'comment')
  • content defined by ACI (details below)
  • (existing) size-column could be defined using ACI as well
• allow to sort by custom columns (or by hardcoded name column)
  • Note: sorting automatically interferes with manually sorting trees (solution: provide 'manual order' as sort criteria; allow order-commands only when manual order is selected)
  • allow to change the order for display (selector in -admin)
    • use that order for all selection lists (update list when order changes)
  • allow to use current display order as new "manual order" (button in -admin)

Implementation details:

Plugin context specific ACI-commands (needs #756) to provide direct access to

• name of used filter
• resulting alignment columns (as proposed by #757)
• name of -reconstruction tool
• other custom (and probably tool-specific) information
  (e.g. used rate-distribution model stored with RAxML-trees)

The plugin-commands have to be smart enough to detect whether -information is present (and what kind of info). Trees generated via external commands AND by more recent arb-versions contain a parse-able format, e.g. something like PRG=RAxML FILTER=termini_5_3/gap_95_mar16 RATE= DIST=GTRGAMMA-25 ALGO=new rapid hill climbing.

• check when this had been introduced into ARB
• if possible, avoid to accept prior format (which might be similar to current!!!)

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requires: #756
required by: #757

[westram]

because required by #757