Please review and comment

Please review and comment.

* removed whitespace added accidentally during rebase

Someone please review and make sure this is now properly corrected.

* updated key image text.

* grammar: repeated word (the the)
* consolidated paragraph for clarity (slight re-write)

* clarification

### Update FAQ
* added key image information (double spend protection)
* clarified Pedersen commitment information

Text from [here](https://www.reddit.com/r/Monero/comments/6wi512/how_can_a_third_party_verify_my_transaction/dm89e8g/).

* grammar:
    * a/an
    * repeated words
    * fragmented sentences
    * possesion
    * run on sentences
    * commas for prepositional phrases
    * is/are conjugations
    * was/were
    * its/it's
    * capitalizing proper nouns (Monero, Bitcoin, etc)
    * formatting (removed linefeeds in middle of sentences)
    * can not/cannot
    * removed commas improperly before conjunctions
* spelling:
    * programmatically
    * hashrate
    * transferring
    * scalability
    * separate
    * transactions
    * additionally
    * particular
    * profitability
    * recommended
    * explicitly
    * separator
    * block
    * drawback
    * favorite
* spelling (br/us)
    * internationalization
    * specialized
    * analyze
    * centralized
    * decentalized
    * memorizing
    * synchronization
    * synchronized

- Added Milestone capabilities
- Added and custom styled comments

typo fix

- Added https:// otherwise it wouldn't redirect properly.

- Reverted link in Contributing to forum.getmonero.org
- Reverted header links to forum.getmonero.org