Deprecate filterGlobal() method

[gedinakova]

Although the method seems to work, it does introduce certain issues with the basic filtering logic and the other filtering UIs.

1. It stringifies all data and applies string conditions which leads to unpredicatable results for non-string columns/fields
2. It confuses the Excel Style Filtering UI to an extent that the whole UI looks broken - the column appears as if filtering is applied but the ESF is not capable of displaying the actual filter (the search component is empty, in most of the cases the Custom filter dialog, too)
3. Applying string conditions on non-string field types breaks the filtering tree rehydration

In general, the method does not seem very practical and useful from an end-user perspective, so we suggest to deprecate it.