Increase consistency in doxygen notation

[kellijohnson-NOAA]

There is a lack of consistency with the doxygen notation that we use and to allow for pattern matching and pulling information out automatically we need to all be consistent. The preferred notation is the "@" symbol, e.g.,

/**
 * @brief
 */

Many files in src/ use the following incorrect notation

/**
 * \file data_object.cpp
 * \brief Implementation of the FIMSLog class and LogEntry struct.
 */

and we also previously had many instances of inline notation, e.g.,

static uint32_t id_g;                    /**< id of the Data Object >*/
fims::Vector<Type> data;                 /**< vector of the data >*/
Type na_value = static_cast<Type>(-999); /**< specifying the NA value >*/

where all documentation, unless it is just a comment, it should be above the object and NOT inline.