main.js: generate translation problems

Automatically create translation problems by randomly picking incorrect
answers from known incorrect translations.

Remove manually created translation problems.
main.js: add ordinal numbers to translations

Add the ordinal numbers to the list of translation problems, this makes
some further work obviously necessary:

- need to move data out to new file
- need to automatically expand male, female, neuter variations
- need to separate number translations from verb translations
Move translation data to new 'data.js'

Introduce a new .js file purely for declaring data, move the large
'translations' array out to this new file so it's easier to switch
between the separate concerns of editing code and editing data.

Note that no code is executed until both .js files are loaded because
the main() function is called by window.onload() after all files have
loaded.
Move non-app specific code to new 'util.js'

Separate the concerns of implementing the logic of game from interacting
with javascript and the browser by splitting non-game specific code into
a new file 'utils.js'.
tidy main.js: move main() to top of file

Re-order 'main.js' so that it reads from more general to more specific
by moving 'main()' to the top of the file.
data.js: add extra array attribute to each word

Prepare to categorise words by introducing a new array attribute into
each word.  This will most likely serve as a container for 'tags' for
each word.

e.g.
     ["I try", "προσπαθώ", ["verb", "present tense"]],