Update variable for property options

[DanPurdy]

closes #966

Added two new options to the variable for property rule
allow-map-get to allow the use of map-get() as a property as this technical references a variable
allowed-functions An array of allowed function names you would like to allow the use of in this rule. i.e. my-map-func() to not throw a linter warning when used as a property value.

A new warning message for functions is now available too
'The function passed to \'' + declarationIdent + '\' is not allowed'

<DCO 1.1 Signed-off-by: Dan Purdy dan@dpurdy.me>

[coveralls]

Coverage increased (+0.01%) to 97.583% when pulling 31d8343 on feature_update-variable-for-property into 658f4c4 on v1-dev.

[coveralls]

Coverage increased (+0.01%) to 97.586% when pulling f142793 on feature_update-variable-for-property into 658f4c4 on v1-dev.