Update ch06.asciidoc

Typos
Dont use github link to line number

If any line above the linked line is ever added or removed from
chainparams.cpp, the link pointing to L.123 will continue to point to
L.123 but the start of the comment won't be there. See
andrew.yurisich.com/work/2014/07/16/dont-link-that-line-number/ for the
workaround i have used on this.
Update ch07.asciidoc

Proposed rephrase of text in "tip box".
corrections, generation Tx, reward calculation, coinbase data
Constructing the block header, difficulty representation
wordsmithing ch02.asciidoc
wordsmithing ch02.asciidoc #2
wordsmithing ch02.asciidoc #3
wordsmithing ch02.asciidoc #4
wordsmithing ch02.asciidoc #5

In the paragraph beginning "Transactions are like lines in a double-entry bookkeeping ledger."  This paragraph needed to be re-written.  It was incorrect from an accounting interpretation.  Debits (meaning "left") are not really on the left side of the graphic and typical display for Inputs in this case, since this is in effect a balance sheet journal entry.  Feel free to double check this with an actual accountant.
wordsmithing ch02.asciidoc #6
wordsmithing ch02.asciidoc #7
wordsmithing ch02.asciidoc #8
wordsmithing ch02.asciidoc #9
wordsmithing ch02.asciidoc #10
wordsmithing ch02.asciidoc #5a

A better wording than "wordsmithing ch02.asciidoc #5"
wordsmithing ch02.asciidoc #11
block header and mining
Merge branch 'chapter/Chapter8' into develop
format fix