Created ChecksumHelper

This allows sha-1 and git checksums to be calculated for strings and files.
Includes unit tests.

re #8924
added ChecksumHelper

re #8924
re #8924 checkpointing work, but alg is functional
re #8924 first version complete with tests
re #8924 Addded rate limit handling
re #8924 improved error handling
re #8924 cppcheck and doxygen fixes
re #8924 solve cmakelist merge issue
re #8924 solve cmakelist merge issue
Use std::string rather than c-style buffers.

Refs #8924
Convert all line endings to UNIX style for git SHA1.

Refs #8924
re #8924 linux warning
Avoid a bug in Poco SecureSocket stack.

The session must be aborted manually before any destructors from
the other objects are called.

It is hard to pin down but at some point between v1.36 & v1.46 the bug
was fixed by ensuring that destructors don't throw exceptions.
Refs #8924
A few tidyups for namespacing, and includes

Also removes hack that didn't work for getting around Poco bug.
Refs #8924
Use jsoncpp to parse JSON files

Also restructured the JSON that is written by us to look a bit more like
github and standard JSON style.
Refs #8924
re #8924 Add doc file
Merge branch 'feature/8924_Intrument_file_repo' of github.com:mantidproject/mantid into feature/8924_Intrument_file_repo
Merge branch 'feature/10550_alg_startup_logging' of github.com:mantidproject/mantid into feature/8924_Intrument_file_repo
re #8924, merge in #10549 and #10550
re #8924 refactor to use InternetHelper