Remove large inline methods from headers

[joelkoz]

In an attempt to minimize the memory footprint of SensESP, a review of memory generation has revealed several inline pieces of code that causes large hunks of memory to be used for mostly redundant code blocks. Audit the header files, and eliminate or move as many inline methods as possible to the .cpp file. The biggest offenders an initial memory inspect has uncovered:

• SensESPApp::connect_1to1_h()
• SKOutput::as_signalk()

[ba58smith]

See @mairas comments in PR #365 before you do this. His findings seem to be contrary to what's stated above.