Minor text updates

[ForNeVeR]

Some things noted in our Awesome list inclusion PR:

• Add information on what F# is (taken some points from Microsoft's What is F# page, might be a bit opinionated but I hope that mostly agreeable).
• Fix capital letters in some items, better punctuation, remove some marketing slogans to make list more up to the point.
• Remove some repetition, such as item name repeating in the item text again.