PERF: perf improvements in DataFrame construction with a non-daily datelike index (GH6479)

Dynamic vbenches
BUG: fix non-caching of some frequency offsets for date generation

DOC: release notes
Merge pull request #6481 from jreback/di_perf

PERF: perf improvements in DataFrame construction with a non-daily datelike index (GH6479)
BUG: Bug in iat/iloc with duplicate indices on a Series (6493)
Merge pull request #6495 from jreback/iat

BUG: Bug in iat/iloc with duplicate indices on a Series (6493)
PERF: perf improvements in single-dtyped indexing (GH6484)
DOC: Clarify that methods taking a MultiIndex level index also accept the name
BUG/TST: read_html should follow pandas conventions when creating empty data
Merge pull request #6447 from cpcloud/read-html-float-iterable-5129

BUG/TST: read_html should follow pandas conventions when creating empty data
DOC: further homogenized the description of "level" argument
DOC: level argument description in _binop
Merge pull request #6500 from toobaz/level_name

DOC: Clarify that methods taking a MultiIndex level index also accept the name
DOC: show users how to emulate R c function with iloc slicing and r_
Merge pull request #6499 from cpcloud/r-slicing-with-c

DOC: show users how to emulate R c function with iloc slicing and r_
TST: windows dtype test fix for tests_indexing/test_imethods_with_dups
Merge pull request #6486 from jreback/reindex

PERF: perf improvements in single-dtyped indexing (GH6484)
PERF: optimize index.__getitem__ for slice & boolean mask indexers
Merge pull request #6440 from immerrr/index-getitem-performance

PERF: optimize index.__getitem__ for slice & boolean mask indexers
BUG: Bug in multi-axis indexing using .loc on non-unique indices (GH6504)
Merge pull request #6506 from jreback/dup_loc

BUG: Bug in multi-axis indexing using .loc on non-unique indices (GH6504)