Add sbr_est() to get estimate (95% CI lower - upper)

[joethorley]

sbr_est(term, x_name, sub, ci = TRUE)

look in tables
ensure term, estimate, lower and upper.
and term should match 1 term only
```sbr_est("bDensity[2]", "coef", "condition")``

[joethorley]

use subfoldr2::sbf_load_table()

[joethorley]

if missing table return SBR_ERR MISSING TABLE or SBR_ERR MISSING VALUE if no term SBR_ERR MULTIPLE VALUES if multiple terms

[joethorley]

should also have type argument where by default term = "table" but could also be "data" or "plot-data"

[joethorley]

add argument to signif figures

[joethorley]

standard should be (95% CI lower - upper)