README cleanups

Hello everyone, I just started playing around with Tor a few days back so as one could expect I started with README.1st.md file. I realized that different *.md files are not consistent style-wise so I decided to clean them up a bit.

Brief summary:

no empty line at the very beginning of the file,
single empty line between sections (sometimes there were two)

... end of the sentence.

New Section
----

rather than

... end of the sentence.


New Section
----

external links use name format,
there is no single space in front of the section name

 Foo
===

is changed to

Foo
===

Which fixes syntax issues in editors like GNU Emacs with enabled markdown preview.

I tried to check all links (local and external) and fix the ones which were broken.

For example the Tor proposal process inside README.1st.md or doc/WritingTests.txt were changed to .../doc/HACKING/WritingTests.md in few places).

At the very end of README.1st.md file there are some TODO (I think?) sections. I wrapped them around in "TODO" section.

TODO
-----------------------

XXXXX also describe

doc/HACKING/WritingTests.md

torguts.git

torspec.git

The design paper

freehaven.net/anonbib

XXXX describe these and add links.

However I am not sure if these are still needed there. Most of these topics are mentioned already in this file and linked to other files (WritingTests, torspec, etc.).

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information