Param names for `src_*` functions should agree with the drivers' names

[bborgesr]

I came across a param name mismatch when I was looking at RMySQL in particular (haven't checked the other drivers):

In DBI, using the RMySQL method for dbConnect, we find the param username:

conn <- DBI::dbConnect(
     drv = RMySQL::MySQL(),
     dbname = "shinydemo",
     host = "shiny-demo.csa7qlmguqrf.us-east-1.rds.amazonaws.com",
     username = "guest",
     password = "guest"
)

# get the first 5 rows:
dbGetQuery(conn, "SELECT * from City LIMIT 5;")
#>    ID           Name CountryCode      District Population
#>  1  1          Kabul         AFG         Kabol    1780000
#>  2  2       Qandahar         AFG      Qandahar     237500
#>  3  3          Herat         AFG         Herat     186800
#>  4  4 Mazar-e-Sharif         AFG         Balkh     127800
#>  5  5      Amsterdam         NLD Noord-Holland     731200

In dplyr, in the src_mysql function, the same param is called user:

my_db <- dplyr::src_mysql(
     dbname = "shinydemo",
     host = "shiny-demo.csa7qlmguqrf.us-east-1.rds.amazonaws.com",
     user = "guest",
     password = "guest"
)

# get the first 5 rows:
my_db %>% tbl("City") %>% head(5)
#>    ID           Name CountryCode      District Population
#>  1  1          Kabul         AFG         Kabol    1780000
#>  2  2       Qandahar         AFG      Qandahar     237500
#>  3  3          Herat         AFG         Herat     186800
#>  4  4 Mazar-e-Sharif         AFG         Balkh     127800
#>  5  5      Amsterdam         NLD Noord-Holland     731200

[krlmlr]

DBI::dbConnect() doesn't specify how the columns should be named, but we may want to follow the majority of DBI drivers.