Apache TsFile 2.0.0

New Feature

• TsFile V4 for Table Model by @jt2594838 in #196
• Support dictionary encoding for STRING data type. by @jt2594838 in #238
• Modify default timestamp encoding by @shuwenwei in #309
• Tsfile java interfaces v4 by @shuwenwei in #307
• Convert column name and table name to lower case by @shuwenwei in #322
• Add type cast interfaces in TsDataType by @jt2594838 in #332

Improvement/Bugfix

• Fix allSatisfy bug in InFilter by @JackieTien97 in #219
• Fix bug in the conversion of int types to timestamp. by @FearfulTomcat27 in #223
• Fix getValue method in Tablet doesn't support Date and Timestamp type by @HTHou in #243
• Fix error when write aligned tablet with null date by @HTHou in #250
• Fix tablet isNull method not correct by @HTHou in #255
• Fixed the issue that the time of the first data item written to TSFile by measurement cannot be a negative number by @luoluoyuyu in #297
• Fix float encoder overflow by @HTHou in #342