apply license and add missing doc.go files
Merge pull request #87 from wongak/86-license

apply license and add missing doc.go files
parameters in constants, prepare execute payment call
schema: add index on paypal tx type
select payment by type
prepare execute payment
refactor init payment to have a general doHttp func
fix url handling
set correct payer id
set correct commit
rework execute payment processing
also log body on http status err
handling of return page
Merge pull request #89 from wongak/paypal_continued

Paypal continued