THRIFT-1980 Go: Modernize go tooling. Update autoconf.

Direct users to use 'go get'
Remove outdated, non-idiomatic Makefiles for Go.
Change 'make check' to run Go tests.
Integrate changes from github.com/pomack/thrift4go

Integrated from 4e1ad38
Update tutorial code for go1
Fix imports: add package prefixes, configurable thrift import.

Avoid generating multiple (invalid) import statements.
Apply astyle formatting
Update error-related language