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ARROW-3760: [R] Support Arrow CSV reader

The main entry point is the `csv_read()` function, all it does is create a `csv::TableReader` with the `csv_table_reader()` generic and then `$Read()` from it.

as in the #2947 for feather format, `csv_table_reader` is generic with the methods:
 - arrow::io::InputStream: calls the TableReader actor with the other options
 - character and fs_path: depending on the `mmap` option (TRUE by default) it opens the file with `mmap_open()` of `file_open()` and then calls the other method.

``` r
library(arrow)
tf <- tempfile()
readr::write_csv(iris, tf)

tab1 <- csv_read(tf)
tab1
#> arrow::Table
as_tibble(tab1)
#> # A tibble: 150 x 5
#>    Sepal.Length Sepal.Width Petal.Length Petal.Width Species
#>           <dbl>       <dbl>        <dbl>       <dbl> <chr>
#>  1          5.1         3.5          1.4         0.2 setosa
#>  2          4.9         3            1.4         0.2 setosa
#>  3          4.7         3.2          1.3         0.2 setosa
#>  4          4.6         3.1          1.5         0.2 setosa
#>  5          5           3.6          1.4         0.2 setosa
#>  6          5.4         3.9          1.7         0.4 setosa
#>  7          4.6         3.4          1.4         0.3 setosa
#>  8          5           3.4          1.5         0.2 setosa
#>  9          4.4         2.9          1.4         0.2 setosa
#> 10          4.9         3.1          1.5         0.1 setosa
#> # … with 140 more rows
```

<sup>Created on 2018-11-13 by the [reprex package](https://reprex.tidyverse.org) (v0.2.1.9000)</sup>

Author: Romain Francois <romain@purrple.cat>

Closes #2949 from romainfrancois/ARROW-3760/csv_reader and squashes the following commits:

951e9f58b <Romain Francois> s/csv_read/read_csv_arrow/
7770ec54c <Romain Francois> not using readr:: at this point
bb13a76e0 <Romain Francois> rebase
83b51621a <Romain Francois> s/file_open/ReadableFile/
959020c91 <Romain Francois> No need to special use mmap for file path method
6e740037d <Romain Francois> going through CharacterVector makes sure this is a character vector
258550143 <Romain Francois> line breaks for readability
0ab839783 <Romain Francois> linting
09187e63b <Romain Francois> Expose arrow::csv::TableReader, functions csv_table_reader() + csv_read()