Set up "Taxonomy data" in the Application Settings

In the current version of the VIROGENESIS framework the taxonomy data are downloaded by the online installer (UGENE-5880) and can't be modified.

Make it possible to modify the data:

• "Taxonomy data" option:
  Add a new option "Taxonomy data" in the UGENE Application Settings.The value is an URL to a folder with taxonomy data (an edit box & the browse button in the GUI).
• Default value:
  The default value should be set to the folder where taxonomy data, downloaded by the installer is located.
• Value modification & validation:
  When a user tries to modify the value, validate that all required files are located in the specified folder. If it is not so, change the edit box background color to pink, disable the "OK" button in the Application Settings dialog (restore the changes, if a correct path is specified).

Also, please verify that CLARK can work with custom taxonomy data in terms of this issue (see UGENE-5959).

TODO: decide smth about duplicate taxonomy files (see e.g. files for the MiniKraken database).