Adding documentation for typical usages of OpenFAST #2286

Job	Run time
build-all-debug-single	3m 50s
build-drivers-release	7m 6s
build-all-debug	6m 43s
build-postlib-release	15m 44s
build-test-uadriver-debug	2m 31s
rtest-modules-debug	7m 31s
rtest-module-drivers	2m 40s
build-openfast-release	5m 16s
build-fastfarm-release	16m 11s
build-interfaces-release	5m 26s
rtest-OF	7m 48s
rtest-OF-5MW_OC4Semi_WSt_WavesWN	1m 19s
rtest-OF-5MW_Land_BD_DLL_WTurb	2m 53s
rtest-OF-5MW_Land_AeroMap	1m 30s
rtest-OF-5MW_OC3Mnpl_DLL_WTurb_WavesIrr	2m 11s
rtest-OF-5MW_OC3Trpd_DLL_WSt_WavesReg	4m 36s
rtest-OF-5MW_OC4Jckt_DLL_WTurb_WavesIrr_MGrowth	1m 38s
rtest-OF-linearization	2m 31s
rtest-OF-simulink	9m 43s
rtest-interfaces	4m 57s
rtest-FF	2m 3s
	1h 54m 7s

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