Greek layout: Add dead key with accent marks and remove polytonic moreKeys

[tenextractor]

This is essentially the "Modern" layout of #203 with a few small changes. The major changes from the old Greek layout are:

• A dead key has been added, with accent marks used in Greek (polytonic accents used in Ancient Greek are in moreKeys)
• There used to be moreKeys with all possible combination of polytonic accents (example: ['α', 'ά', 'ὰ', 'ᾶ', 'ἀ', 'ἁ', 'ἄ', 'ἅ', 'ἂ', 'ἃ', 'ἆ', 'ἇ', 'ᾳ', 'ᾴ', 'ᾲ', 'ᾷ', 'ᾀ', 'ᾁ', 'ᾄ', 'ᾅ', 'ᾂ', 'ᾃ', 'ᾆ', 'ᾇ']). This has been mentioned as an issue, and they are not even used in modern Greek, so they have been removed.

[tenextractor]

There is already #203 , however, not only has it been idle for a while, but it also has the polytonic layout which I have some (minor) issues with. I think the issue of Polytonic Greek can be addressed later, while the lack of a dedicated key for the acute accent is a far more important issue, as it appears in every word which has two or more syllables.