Add readout for mechanics

Add the ability to read mechanics.txt files which describe string mechanics.

src/KM3io.jl

@@ -21,7 +21,7 @@ export ROOTFile
 export H5File, H5CompoundDataset, create_dataset, addmeta
 
 export Direction, Position, UTMPosition, Location, Quaternion, Track, AbstractCalibratedHit
-export Detector, DetectorModule, PMT, Tripod, Hydrophone, StringMechanics, center, isbasemodule, getmodule, modules, getpmt, getpmts
+export Detector, DetectorModule, PMT, Tripod, Hydrophone, StringMechanics, StringMechanicsParameters, center, isbasemodule, getmodule, modules, getpmt, getpmts
 
 # Acoustics
 export Waveform, AcousticSignal, AcousticsTriggerParameter, piezoenabled, hydrophoneenabled