Add SRS Function Generator

Add a simple device to control a SRS DS345 Function Generator
Continue implementing SRS device
Finished Display Info, Init Device, and Get Picture
Added device name to amplitude/offset error
Merge branch 'master' into add-SRS-Funct-Generator
Add new VIs required for override, move Get Picture into class
Made Single Val Columns used not Rampeable
Merge branch 'master' into add-SRS-Funct-Generator
Incorporated MenuCol
Set MenuCol Defaults for SRS
Merge branch 'master' into add-SRS-Funct-Generator

Conflicts:
	codes/DeviceVIs/Utils_devs/AddDevice.vi
	codes/TypeDefs/AddDeviceRing.ctl

Took the version from master for both of the above, and also added SRS
DS345 as last case in ImplementedDevices.vi to handle the equivalent
function of adding the SRS to the Add Device menu.
Add DBLtoMenuItem.vi as a helper for MenuCol

Because users may want to allow variables to select items normally chosen
from a menu, DBLtoMenuItem converts a passed double value n (like from Lua's
Str2DBL.vi) to the round(n)th menu item text (0-indexed).  That is,
passing a value of 0.0 would get the top menu item, 1.0 the next one, etc.
Fixed missing tunnel assignment on DBLtoMenuItem

Forgot to set output to default to empty string on the error case.
Use SingleValMenuCol instead of MenuCol
addresses #23 request: display start/end values
Move VI's to reflect new device structure

Also edit error descriptions
Merge branch 'master' into add-SRS-Funct-Generator
Merge remote-tracking branch 'origin/master' into improve-layout-portability