Expand on Bulgarian entries & restructure contents

[VTIvanov20]

Synopsis:

I have added additional forms of the word "thirteen" in Bulgarian, as well as a new structure for their organisation.

Structure:

1. Official base of the word

   • Countable / Plural form
   • Actions, that are not performed by the sentence's main subject (masculine -> feminine -> gender neutral)
   • Action that are performed by the sentence's main subject (masculine -> feminine -> gender neutral)

2. Official slang base of the word

   • Countable / Plural form
   • Actions, that are not performed by the sentence's main subject (masculine -> feminine -> gender neutral)
   • Action that are performed by the sentence's main subject (masculine -> feminine -> gender neutral)

(Every entry also has a commented clarification on what its' function is.)

Free to discuss any suboptimal entries, if anything pops up. Have a nice day! :)