Revert "add .equal to tolerantly compare two numeric vectors; fixes #24"

This reverts commit e409f1e713ea6e3a36dc83fefb3adb5f01360bcf.
Revert "change test case to show a warning (rounding problem in "anyMissing"; see #24)"

This reverts commit b1c4f63647e3907902f1f9132a00d7a0d8e4d33d.
Revert "integrate .anyMissing in .validMassSpectrum and adapt test cases; fixes #23"

This reverts commit 472c469198acf468a61e48882bd40ddf82da1f80.

Conflicts:
	DESCRIPTION
	NEWS
	man/MALDIquant-package.Rd
Revert "add anyMissing to test for missing data"

This reverts commit 54a5d0d83f95866a350bb1d1365bd45b8e126fd4.
simplify and speed up isEmpty