A few more bitcoin -> dogecoin in build-unix.md

Pretty simple.  Should BITCOIN_ROOT be changed?
Merge pull request #623 from whitj00/patch-2

Replace occurrences of "bitcoin" with "dogecoin" in the UNIX build instructions.
Update bitcoin_zh_CN.ts

Update Chinese translation of 'Dogecoin'
Merge pull request #625 from 51doge/patch-3

Update bitcoin_zh_CN.ts
Change Bitcoin to Dogecoin
Change Bitcoin to Dogecoin
Merge pull request #631 from PartTimeLegend/patch-2

Change Bitcoin to Dogecoin
Merge pull request #630 from PartTimeLegend/patch-1

Change Bitcoin to Dogecoin