AH (Ad Hoc) waveform format read support

AH v1 should be fine.
AH v2 tests need some real examples + ASCII equivalents to finish this PR - unfortunatly I couldn't find anything useable :/

Anyone got some AH v2 files? @jsaul, @jwassermann?
those typos also exist in the files ```BRV.TSG.DS.lE21.asc``` and ```BRV.TSG.KSM.sE12.asc```- which are probably generated by some AH2ASC script - I don't want to touch this data as this is downloaded as it is from http://www.ldeo.columbia.edu/res/pi/Monitoring/Data/ - if its really bothering you - go ahead ;)