OPENDJ-1802 Address review comments about "Make ByteStringBuilder methods"

TimeBasedMatchingRulesImpl.java, core.properties:
Used:
- byte instead of int for encoding second, minute, day and month.
- compact unsigned instead of int for encoding year.
Replaced all mentions of 'date' by 'day'.
Replaced ByteBuffer with ByteSequenceReader.

AbstractSubstringMatchingRuleImpl.java:
Used byte instead of int for encoding ASCII chars.
In evaluateEscapedChar(), changed return type from char to byte.
In evaluateEscapes(), extracted method evaluateEscapes0().

*.java:
Removed now useless uses of '& 0xFF'