Fix #3

[ilyaZar]

Fix #3

Add several name-watchers for on()

• provides the "or" case
• provide an expression generator generate_watch_expr() that parses "name" arg to a list of reactives
• each element of this list is put into observeEvent
• if length(name) == 1, the default (previouis) behaviour is used

Restyle with grkstyler.

see edb8c82e0786d7f9ed3bf9ca1749914ed188faed

[ilyaZar]

edit PR:

• update docstring: see 311fc7b384ef86b6cff20c2e1143fa24f2864c05

• add session = session for watch()-call inside on() in light of #17 and #18: see edb8c82e0786d7f9ed3bf9ca1749914ed188faed

• add a finer error message that only prints those event-flags that are actually uninitialized f84c03d6def01cc7244a7bf160b30944d38c86d5

• add tests for the case where name argument for on() is a vector e16ff21036c547c4a369b35db5a668a22bd444cb

  • if merged with #20 will keep test coverage for {gargoyle} at 100% !!