CRAN release (tidyverse#3082)

Move build/run time checks to dr_dplyr

Update site

Update for CRAN submission

Update sql docs

Prepare for release

- Functions related to `tbl` and `src` stay in `dplyr` (tidyverse#26)…

…. Remove unused `make_tbl()`.

- Non-scalar input to `frame_data()` and `tibble()` (including lists) creates list-valued columns (tidyverse#7).
- Use C++ implementation for `as_data_frame.matrix()` (tidyverse#14). Also add former `matrixToDataFrame()` tests, and fix unwanted conversion to factor.
- `as_data_frame(NULL)` is 0-row 0-column data frame (tidyverse#17, @jennybc). `frame_data()` and `tibble()` create empty `data_frame` if no rows are given (tidyverse#20).
- `data_frame(NULL)` raises error "must be a 1d atomic vector or list".
- `lst(NULL)` doesn't raise an error anymore (tidyverse#17, @jennybc), but always uses deparsed expression as name (even for `NULL`).
- `trunc_mat()` and `print()` use `width` argument also for zero-row and zero-column data frames (tidyverse#18).
- `glimpse()` now (invisibly) returns `x`, so it can be used within a chain of `dplyr` verbs (@edwindj).
- `base::getElement()` now works with tibbles (tidyverse#9).
- Remove spurious usage of "dplyr" in documentation (tidyverse#3).
- Almost full test coverage.

- `frame_data()` forces list-mode columns if length-one lists are giv…

…en as input.

- Add tests for `matrixToDataFrame()`.
- `glimpse()` now (invisibly) returns `x`, so it can be used within a chain of `dplyr` verbs (@edwindj).

- Functions related to `tbl` and `src` stay in `dplyr` (tidyverse#26).

- `data_frame(NULL)` raises error "must be a 1d atomic vector or list".

- Non-scalar input to `frame_data()` and `tibble()` creates list-valu…

…ed columns (tidyverse#7).

- `frame_data()` and `tibble()` create empty `data_frame` if no rows are given (tidyverse#20).
- `as_data_frame(NULL)` is 0-row 0-column data frame (tidyverse#17, @jennybc).
- `lst(NULL)` doesn't raise an error anymore (tidyverse#17, @jennybc), but always uses deparsed expression as name (even for `NULL`).
- `trunc_mat()` and `print()` use `width` argument also for zero-row and zero-column data frames (tidyverse#18).