Human readable duration search

Addresses this (https://bugs.launchpad.net/mixxx/+bug/1261493) wishlist bug

MIXXX can only search duration in seconds.
Searching tracks with duration keyword is made more natural. User can
search now in following formats

2:30/2:30m
2:30:45/2:30:45h
2m30s/2m30
2h30m45s/2h30m45

In user manual we should encourage our users to use top two formats.
Humanreadable duration search enabled
REF: use 'else if' instead of boolean check
Create dedicated duration query node

Duration does not accept only a simple numeric value anymore. Instead
handle it as a special search note.
REF: time string parsing

Parse directly with a qregexp. Simplify the code. This also changes the
format of time strings that are supported. To search for a track of
exactly 90 seconds the following terms are equivalent.

90
90s
1m30
1m30s
1:30

searching for 62 seconds can be entered as

62
62s
1m2
1m2s
1m02s
1:2
REF: deduplicate Code

DurationFilterNode is now a child of NumericFilterNode. The can share
the same toSql and match functions once the argument is parsed.
Update translation template. Found 1766 source text(s) (23 new and 1743 already existing).
VCI400: hook up fx enable buttons to the two units, also make the knob
the mix control.
Merge branch 'VCI400' into DJO-hacks-trunk
Fix master sync so if the current deck is playing, don't match bpm to non-playing deck.
Merge branch 'master' into DJO-hacks-trunk
VCI400: More tweaks based on usage.
Merge branch 'VCI400' into DJO-hacks-trunk
Protect against decks with 0 bpm participating in the sync process.
FIX: 1349173 dlgtagfetcher apply updates dlgtrackinfo
dlgtrackinfo apply updates dlgtagfetcher m_track
listen to track signals to update metadata display
Merge pull request #306 from kain88-de/fix1349173

Update Tagfetcher about changes in TrackInfo and vice versa
REF: parseTime, remove qDebug statement
REF: use init method in NumericFilterNode

To deduplicate code the numeric filter now uses a init function and a
generic 'parse'. This way any child class of NumericFilterNode only has
to reimplement the parse function.