bladeRF-cli: Renamed input interface functions

Previously this was only for interactive mode support, and has since
grown to include scripting support. Following commits will include
support for commands specified via the command. As such, this renaming
is intended to clear up misnomers before further adding to any
confusion.
bladeRF-cli: Changed CMD_RET_* -> CLI_RET_* and similar fn renaming

This is another non-functional, code cleanup (yak shaving) item.

The CMD_RET_* codes are now used throughout the CLI and not just in
commands. Therefore, they have been moved to common.h and renamed
appropriately. Similar changes have been made with functions like
cmd_strerror() -> cli_strerror().
bladeRF-cli: Added -e <command> support

This option allows interactive mode commands to be executed from the
command line. Multiple -e <cmd> arguments may be provided; they will be
executed in the order they are specified.

Operations/command are performed in the following order:
    - Command line options (e.g., FPGA load, firmware flash)
    - Commands from '-e <cmd>' arguments
    - Commands from script files
    - Interactive mode commands
bladeRF-cli: Differentiate between file "not found" and I/O errors
bladeRF-cli: Cleaned up items reported by Clang static analysis

tx.c - Removed dead assignment, fixed leak due to incorrect status check
main.c - Memory leaks in rc_config items
conversions.c - Removed dead assignment
script.c - fileno() doesn't fail when given valid FILE*. Removed false positive.
libbladeRF: Addressed items identified by Clang scan

tests/test_sync/src/test.c:
    Changed sample buffer type to int16_t. These alleivates noise from static
    analysis tools regarding a type mismatch with sizeof(), and better
    exemplifies the buffers that should be used in conjunction with the SC16 Q11
    format.

tests/test_repeater/src/repeater.c:
    Fixed unchecked pthread_cond_wait result.

tests/test_async/main.c:
    Fixed unchecked return values, minor cleanup.

src/lms.c:
    Removed dead assignment.

src/backend/usb/usb.c:
    Corrected unchecked return value.

src/backuend/usb/libusb.c:
    Fixed uninitialized variable in error path.