arrow

ARROW-3842: [R] RecordBatchStreamWriter api

This ended up being more than anticipated. In this PR, trying to get closer to the pyarrow api.

-  Using active bindings instead of methods for things that are exposed as properties in python
- Using a factory function with the same name as the class name, e.g.. `arrow::RecordBatchFileWriter` gets a `RecordBatchFileWriter` function

This is fairly benign even though it's a big pr, it's mostly mechanical.

@javierluraschi this probably affects code that e.g. uses `$schema()` and now should use `$schema` etc ...

- `read_record_batch` now always need a `schema`
- `write_table` and `write_record_batch` are gone, and replaced with `write_arrow` which uses either the streaming format or the binary file format depending on the `stream` parameter:

    - `arrow::ipc::RecordBatchStreamWriter` : streaming format
    - `arrow::ipc::RecordBatchFileWriter` : binary file format
    - `character` : file format
    - `fs_path` : file format
    -  `raw` : streaming format

    it's always possible to construct a RecordBatchStreamWriter or a RecordBatchFileWriter from an InputStream of your choice if these defaults don't work, but I believe they make sense.

Author: Romain Francois <romain@purrple.cat>

Closes #3043 from romainfrancois/ARROW-3842 and squashes the following commits:

01517e753 <Romain Francois> handle C_VISIBILITY at configure time.
e9889114d <Romain Francois> more converting public to active
d11c175c6 <Romain Francois> doc fixes
eed49297e <Romain Francois> doc fixes
ac0528d3c <Romain Francois> methods -> active
a7d73066b <Romain Francois> DataType$id and FixedWidthDataType$bit_width become active (as in pyarrow)
f62a22d31 <Romain Francois> Move more things to active rather than methods, to match pyarrow
590002079 <Romain Francois> + Table$columns(), RecordBatch$columns()
cc9669519 <Romain Francois> num_rows, num_columns, and schema become active rather than methods (as in pyarrow api)
77916c5d7 <Romain Francois> -doc directory
6f5db727c <Romain Francois> document read_arrow with read_table
f16f1267a <Romain Francois> update documentation for read_table
2dcca0345 <Romain Francois> write_arrow replaces write_table and handles Table, RecordBatch and data.frame, thanks to the unexported dispatcher to_arrow
1ea3b558f <Romain Francois> + method $batches() in RecordBatch(Stream|File)Reader
79192cb4b <Romain Francois> rename BufferOutputStream$Finish to $getvalue, as in pyarrow
f1af42e84 <Romain Francois> using lower case methods, like in pyarrow
740352d35 <Romain Francois> refactoring