Add multipucker action

[drroe]

Version 5.3.3

This adds the multipucker action. Similar to multidihedral, multipucker will search for specified pucker types in a given residue range and automatically set up and calculate the pucker. Addresses #893.

  [help multipucker]
	[<name>] [<pucker types>] [resrange <range>] [out <filename>]
	[altona|cremer] [puckertype <name>:<a0>:<a1>:<a2>:<a3>:<a4>[:<a5>] ...]
	[amplitude [ampout <ampfile>]] [theta [thetaout <thetafile>]]
	[range360] [offset <offset>]
	<pucker types> =  nucleic furanose pyranose

Adds a test and manual entry for this.

This PR also does the following:

• Fix segfault when doing info commands with no topology loaded.
• Avoid divide by zero in nativecontacts PDB output when no native contacts detected.
• Adds a note about GMXDATA environment variable to address GMXDATA variable needs to be documented. #901.

[lgtm-com]

This pull request introduces 1 alert when merging 186f38e into 46b3c7e - view on LGTM.com

new alerts:

• 1 for Too few arguments to formatting function