Add links to how.bitshares.works after it's ready

[abitmore]

Places that I've thought of:

• README
• Wiki

[cedar-book]

@abitmore, I have moved all wiki contents in dev.bitshares.works repository. Some contents were "ideas" or "todos". I put together those contents in this page. If you are okay, I can move links one by one. If you have links, want to wait to switch I won't do that.

[oxarbitrage]

with this #1031 done we can drive our attention here.

[oxarbitrage]

added link to dev portal at wiki https://github.com/bitshares/bitshares-core/wiki front page.

"New and updated developer information can be found at Bitshares Developer Portal"

[cedar-book]

Very beginning (in May), I started to use "how.bitshares.works" repository instead of "dev.bitshares.works" repository for the developers documentation.
If I remember correctly, this request was "after BitShsares-Core repository's Readme and wiki's contents were moved to new doc location (in dev.bitshares.works), replace current wiki's link to the new content location."

Currently, the dev.bitshares.works documents source files are RST format to build the html. I have moved most of them, some of them are mixed with others or in Tutorials/FAQs. And if I could not find a good group section to add, I put all on a wiki legacy page in Knowledge Base section.
Probably, we can move (archive) some old contents to the wiki legacy page to reduce clutter?

I created this contribution guide (in July). It will be updated.

[abitmore]

Fixed by #1363.