Spell-Check: Enable user to add dictionary entries

Issue general description

LanguageTool integration: Enable user to add words to a customer specific dictionary or to a task specific dictionary.

Used dictionaries for a task

• For each customer and for each task a dictionary is automatically created in the languageTool instance, if none exists on first usage (languageTool does that automatically, when first adding a word to a non-existing dict).
• When a task is edited, automatically the customer and the task specific dicts are used.
• When a termCollection is created, for each target-language in the termCollection a dictionary is created and automatically all terms are added as dictionary for that language to languageTool.
• When a termCollection gets assigned to a task, its dictionary is used for the task, too.
• When a term is added or updated, that change is also reflected in the relevant dictionary, that corresponds to the termCollection. (Do not synch Term-Proposals, only "finalized" and "provisionally processed" terms.)

Add words to a dictionary in the editor GUI

Enable user to add words to

• a customer specific dictionary
• a task specific dictionary

This should be possible from the editor:

• by right-click on a spelling error: new options in the list (extra look): „Add to task dict.“, „Add to customer dict.“
• by click on a new button „Administrate dictionary“ (s.u.)

Administrate dictionary (add and delete words)

• new button „Administrate dictionary“ (= in opened task next to button ‚Leave task‘; open new pop-up when clicked)
• in the pop-up: list all words from the dictionaries of this task and its customer in a grid (= without termCollection-dictionaries)
• show infos about the specific dictionary in extra column: Type ‚task‘ or customer-name
• be able to filter the grid
• be able to add words into the dictionaries: add button “Add word”, open new window, create form (new word, option-list for task-/cust-dict, "Save changes"-button)
• be able to delete words from the list (one by one is ok, but NOT with reload from the grid and the user needs to scroll again etc!!!...)
• click on button "Save changes" to really delete the words in LT-dictionaries (otherwise changes are lost, eg by just closing the popup)

Define, who is allowed to edit a dictionary

Task-specific dictionaries can be edited by everyone, who is assigned to a task with edit rights.

Who can edit customer-specific dictionaries is defined in the user management as a role. (Administration of customer-specific dictionaries also only via tasks.)

Ensure, terms are not marked as errors

Architecture questions

The rest API documented here can be used: https://languagetoolplus.com/http-api

LanguageTool itself uses a database. The languageTool developers will provide us with the database structure so we can set up translate5's own local languageTool REST API based on the database and with a REST API analogous to  https://languagetoolplus.com/http-api.