[Feature] \scan command

**Introduction**
Sometimes, there is no need to update filter, we might want to scan memory several times using the same filter with the same values. For example, it is absolutely not needed for filter `FilterChange` where `x[t - 1] != x[t]`, no need to call command `\update_filter` since there is nothing to update.

**Description**
`\scan` command should be introduced in order to scan memory using the same filter.

Consider to implement `\repeat` instead.

**Relations**
Related to:
- #69