[datadict] Fix missing variables & ignore meta fields

[ridz1208]

Brief summary of changes

Just some fixes that were necessary on CBIG to be able to build the dictionary

1. ignore .meta fields for LINST files
2. re-add DATA ENTRY common filed to all instruments
3. make the script runnable from anywhere

TODO if I get time make the script check if the instrument is an instance of the Instrument class rather than pattern matching on 'extends NDB_BVL_Instrument'

Testing instructions (if applicable)

Link(s) to related issue(s)

• Resolves # (Reference the issue this fixes, if any.)

[ridz1208]

@jeffersoncasimir did we have other headers toignore here?

[driusan]

@ridz1208 Failing tests

[nicolasbrossard]

Tested on my VM:

1. jsondata and norules ignored
2. Data_entry field added to data dictionary.

LGTM