Document SynchroAttribute columns

[Hipska]

This adds possibility to let data collectors know which column names are available to be synchronised.

Problem:

• Sometimes the column name is not the same as iTop attribute code
• Sometimes an attribute has multiple columns (Blob, ...)

See also counterpart PR Combodo/itop-data-collector-base#37.

[Hipska]

Can we have some feedback please?

[Hipska]

Anyone?

[jf-cbd]

Hello @Hipska, thanks for the PR, and sorry for the delay.
Answering here for the current PR and Combodo/itop-data-collector-base#37.
Functionally, your PR is very interesting.
Technically, we'll perform a check and come back to you soon because we have a few concerns about performances (e.g.memory limit used by collector) and interface.