Export all pages, simplified datefrom, and suppress fix

[diabolusss]

• export: append exported range timestamp to filename
• filter: dateto/datefrom add support for offset from current date, i.e. datefrom:T00:00:00 dateto:T01:00:00, datefrom:\-2T, datefrom:\-1T01
• fixed BUG: "Suppress duplicated messages" + add property to control distance between duplicates
• GUI: if suppress is enabled, then show how much records were suppressed (LN_GEN_SUPPRESSEDRECORDCOUNT)
• $CFG[ExportSuppressDuplicatedMessages] - separate export suppressing from view
• $CFG[ExportAllMatchPages] - allow to control how much to export by default
• $CFG[DuplicateRecordMaxTsDistance] - check duplicates timestamp before suppressing, i.e. same message with 24h period may not be assumed as duplicate

[diabolusss]

@alorbach please, check this pull request.